Conventionally, various technologies for detecting information about an object seated on a vehicle seat by using a photographing device such as a camera are known. For example, disclosed in Japanese Patent Unexamined Publication No. 2003-294855 is a configuration of an occupant detecting apparatus in which a single camera arranged in front of a vehicle occupant is used to detect the position of the vehicle occupant.
With the technology for detecting information about a vehicle occupant by using a single camera such as the occupant detecting apparatus disclosed in Japanese Patent Unexamined Publication No. 2003-294855, however, it is difficult to address the request for detecting about a plurality of vehicle occupants because the camera has a limitation on its viewing angle. To address the request, the technique using a wide-angle lens or a fish-eye lens has been proposed as a technology for detecting information about a plurality of vehicle occupants. With this technique, however, it is required to compensate distortion in image due to the wide angle. Accordingly, there is a problem of increasing the complexity and size of the apparatus.